Spontaneous changes in mandibular incisor crowding from mixed to permanent dentition: a systematic review

INTRODUCTION

Dental crowding is the most prevalent malocclusion in the mixed and permanent detitions and can have a major impact on dentofacial esthetics. However, adjustments to the development and growth of the dentition can potentiate self-correction of dental crowding during childhood.

OBJECTIVE

To evaluate the physiological behavior of mandibular incisor crowding in the transition from mixed to permanent dentition.

METHODOLOGY

Five electronic databases (PubMed, Scopus, Web of Science, LILACS and LIVIVO) and part of the gray literature (Proquest and Google Scholar) were investigated, based on the eligibility criteria associated with the acronym PECO, until June 2022. The risk of bias was assessed using the ROBINS-E tool and the certainty of evidence, the GRADE tool.

RESULTS

Among the 2.663 studies identified, five were selected for qualitative analysis, of which one have a low risk of bias, and four, a moderate risk. A total of 243 patients were evaluated. Evidence with a high level of certainty was generated indicating a tendency for improvement in mandibular incisor crowding from mixed to permanent dentition, with mandibular incisor crowding decreasing from 0.17 to 4.62 mm on average. The mandibular incisor crowding reduction seems to be associated with the amount of initial crowding and spontaneous dental arch dimensional changes that occur in the mixed dentition and culminate in the increase in arch perimeter, leeway space, incisor protrusion and transverse growth of the maxillary and mandibular arch.

CONCLUSION

Based on moderate scientific evidence, spontaneous longitudinal changes in dental arch in the transition from the mixed to the permanent dentition demonstrate a spontaneous improvement in mandibular incisor crowding by up to 4.62 mm. These evidence provide a scientific basis for planning only longitudinal follow-up in patients with mild to borderline moderate mandibular incisor crowding in the mixed dentition avoiding overtreatment.

Mandibular Crowding: Diagnosis and Management-A Scoping Review

BACKGROUND

Crowding is the most frequent malocclusion in orthodontics, with a strong hereditary tendency. It already occurs in pediatric age and is mainly hereditary. It is a sign of a lack of space in the arches, and is not self-correcting, but can worsen over time. The main cause of the worsening of this malocclusion is a progressive and physiological decrease in the arch perimeter.

METHODS

To identify relevant studies investigating the most common possible treatments for mandibular dental crowding, a comprehensive search of PubMed, Scopus and Web of Science was conducted encompassing the last 5 years (2018-2023) using the following MeSH: "mandibular crowding AND treatment" and "mandibular crowding AND therapy ".

RESULTS

A total of 12 studies were finally included. An orthodontic treatment cannot ignore the concept of "guide arch", which concerns the lower arch, because of the objective difficulty in increasing its perimeter; the bone structure of the lower jaw is more compact than that of the upper one. Its expansion, in fact, is limited to a slight vestibularization of the incisors and lateral sectors that may be associated with a limited distalization of the molars.

CONCLUSIONS

There are various therapeutic solutions available to the orthodontist, and a correct diagnosis through clinical examination, radiographs and model analysis are essential. The decision of how to deal with crowding cannot be separated from an overall assessment of the malocclusion to be treated.

IPR treatment and attachments design in clear aligner therapy and risk of open gingival embrasures in adults

BACKGROUND

The incidence of open gingival embrasures (OGE) in patients after fixed appliance treatment is relatively high, while there are no detailed reports on patients after clear aligner therapy. Also, no clinical studies with large sample size have investigated whether interproximal enamel reduction (IPR) can actually avoid OGE. The purpose of this study was to determine the prevalence of OGE in adults after clear aligner therapy and to investigate the risk of OGE associated with IPR treatment and attachment design, focusing on the amount and distribution in mandibular anterior teeth.

METHODS

Pre-treatment and post-treatment intraoral frontal photographs of 225 non-extraction patients were evaluated retrospectively for the occurrence and severity of OGE. The amount of IPR and the number of attachments in the anterior teeth from subjects after screening were recorded according to the first version of clear aligner software (Clincheck, San Jose, USA) and clinical medical documents. Logistic regression analysis was performed to identify the factors contributing to OGE.

RESULTS

The incidence of OGE in non-extraction patients after clear therapy between maxillary and mandibular central incisors was 25.7% and 40.3%, respectively. IPR was not associated with the occurrence of OGE but was associated with severity (P < 0.05). The number of attachments in the anterior teeth or central incisors was significantly related to the incidence of OGE (P < 0.05) but was not associated with severity.

CONCLUSION

A high rate of OGE occurs after clear aligner therapy. Clinicians should be aware of the application of IPR and the design of attachments during clear aligner therapy.

Alveolar bone morphology in patients with a unilateral palatally displaced maxillary lateral incisor: A cone-beam computed tomography study

INTRODUCTION

Lingual displacement of the maxillary anterior teeth is 1 of the most common forms of malocclusion. The labial alveolar bone is thinner for the maxillary lateral incisor than for the central incisor and canine; however, the alveolar bone width at the actual position of the maxillary lateral incisor has not been examined. We investigated the morphologic characteristics of the alveolar bone around palatally displaced maxillary lateral incisors using cone-beam computed tomography and a split-mouth model.

METHODS

Twenty-seven patients with a unilateral palatally displaced maxillary lateral incisor were included. Axial, sagittal, and horizontal measurements were recorded at 3 levels (ie, 25%, 50%, and 75% of the root length) using cone-beam computed tomography. All obtained data were statistically analyzed using paired t tests.

RESULTS

The labial alveolar bone width at 25% of root length was significantly lesser on the affected side. At all 3 levels, the distance between a line tangential to the labial alveolar bone of the central incisor and canine and the position of the labial alveolar bone of the lateral incisor was significantly greater on the affected side. At 50% and 75% of root length, the horizontal distance between the posterior nasal spine and the labial alveolar bone of the lateral incisor was significantly lesser on the affected side.

CONCLUSIONS

Palatal displacement of maxillary lateral incisors is significantly associated with decreased alveolar bone width at the apical level and asymmetry. However, a further elaborate investigation is necessary to determine the clinical relevance of the study.